examples/webgl_portal.html

<!DOCTYPE html>
<html lang="en">
	<head>
		<title>three.js webgl - portal</title>
		<meta charset="utf-8">
		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
		<link type="text/css" rel="stylesheet" href="main.css">
		<style>
			body {
				color: #444;
			}
			a {
				color: #08f;
			}
		</style>
	</head>
	<body>

		<div id="container"></div>
		<div id="info"><a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> - portal
		</div>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import * as CameraUtils from 'three/addons/utils/CameraUtils.js';
			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';

			let camera, scene, renderer;

			let cameraControls;

			let smallSphereOne, smallSphereTwo;

			let portalCamera, leftPortal, rightPortal, leftPortalTexture, reflectedPosition,
				rightPortalTexture, bottomLeftCorner, bottomRightCorner, topLeftCorner;

			init();

			function init() {

				const container = document.getElementById( 'container' );

				// renderer
				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.setAnimationLoop( animate );
				renderer.localClippingEnabled = true;
				renderer.toneMapping = THREE.ACESFilmicToneMapping;
				container.appendChild( renderer.domElement );

				// scene
				scene = new THREE.Scene();

				// camera
				camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 1, 5000 );
				camera.position.set( 0, 75, 160 );

				cameraControls = new OrbitControls( camera, renderer.domElement );
				cameraControls.target.set( 0, 40, 0 );
				cameraControls.maxDistance = 400;
				cameraControls.minDistance = 10;
				cameraControls.update();

				//

				const planeGeo = new THREE.PlaneGeometry( 100.1, 100.1 );

				// bouncing icosphere
				const portalPlane = new THREE.Plane( new THREE.Vector3( 0, 0, 1 ), 0.0 );
				const geometry = new THREE.IcosahedronGeometry( 5, 0 );
				const material = new THREE.MeshPhongMaterial( {
					color: 0xffffff, emissive: 0x333333, flatShading: true,
					clippingPlanes: [ portalPlane ], clipShadows: true } );
				smallSphereOne = new THREE.Mesh( geometry, material );
				scene.add( smallSphereOne );
				smallSphereTwo = new THREE.Mesh( geometry, material );
				scene.add( smallSphereTwo );

				// portals
				portalCamera = new THREE.PerspectiveCamera( 45, 1.0, 0.1, 500.0 );
				scene.add( portalCamera );
				//frustumHelper = new THREE.CameraHelper( portalCamera );
				//scene.add( frustumHelper );
				bottomLeftCorner = new THREE.Vector3();
				bottomRightCorner = new THREE.Vector3();
				topLeftCorner = new THREE.Vector3();
				reflectedPosition = new THREE.Vector3();

				leftPortalTexture = new THREE.WebGLRenderTarget( 256, 256 );
				leftPortal = new THREE.Mesh( planeGeo, new THREE.MeshBasicMaterial( { map: leftPortalTexture.texture } ) );
				leftPortal.position.x = - 30;
				leftPortal.position.y = 20;
				leftPortal.scale.set( 0.35, 0.35, 0.35 );
				scene.add( leftPortal );

				rightPortalTexture = new THREE.WebGLRenderTarget( 256, 256 );
				rightPortal = new THREE.Mesh( planeGeo, new THREE.MeshBasicMaterial( { map: rightPortalTexture.texture } ) );
				rightPortal.position.x = 30;
				rightPortal.position.y = 20;
				rightPortal.scale.set( 0.35, 0.35, 0.35 );
				scene.add( rightPortal );

				// walls
				const planeTop = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0xffffff } ) );
				planeTop.position.y = 100;
				planeTop.rotateX( Math.PI / 2 );
				scene.add( planeTop );

				const planeBottom = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0xffffff } ) );
				planeBottom.rotateX( - Math.PI / 2 );
				scene.add( planeBottom );

				const planeFront = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0x7f7fff } ) );
				planeFront.position.z = 50;
				planeFront.position.y = 50;
				planeFront.rotateY( Math.PI );
				scene.add( planeFront );

				const planeBack = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0xff7fff } ) );
				planeBack.position.z = - 50;
				planeBack.position.y = 50;
				//planeBack.rotateY( Math.PI );
				scene.add( planeBack );

				const planeRight = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0x00ff00 } ) );
				planeRight.position.x = 50;
				planeRight.position.y = 50;
				planeRight.rotateY( - Math.PI / 2 );
				scene.add( planeRight );

				const planeLeft = new THREE.Mesh( planeGeo, new THREE.MeshPhongMaterial( { color: 0xff0000 } ) );
				planeLeft.position.x = - 50;
				planeLeft.position.y = 50;
				planeLeft.rotateY( Math.PI / 2 );
				scene.add( planeLeft );

				// lights
				const mainLight = new THREE.PointLight( 0xe7e7e7, 2.5, 250, 0 );
				mainLight.position.y = 60;
				scene.add( mainLight );

				const greenLight = new THREE.PointLight( 0x00ff00, 0.5, 1000, 0 );
				greenLight.position.set( 550, 50, 0 );
				scene.add( greenLight );

				const redLight = new THREE.PointLight( 0xff0000, 0.5, 1000, 0 );
				redLight.position.set( - 550, 50, 0 );
				scene.add( redLight );

				const blueLight = new THREE.PointLight( 0xbbbbfe, 0.5, 1000, 0 );
				blueLight.position.set( 0, 50, 550 );
				scene.add( blueLight );

				window.addEventListener( 'resize', onWindowResize );

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			function renderPortal( thisPortalMesh, otherPortalMesh, thisPortalTexture ) {

				// set the portal camera position to be reflected about the portal plane
				thisPortalMesh.worldToLocal( reflectedPosition.copy( camera.position ) );
				reflectedPosition.x *= - 1.0; reflectedPosition.z *= - 1.0;
				otherPortalMesh.localToWorld( reflectedPosition );
				portalCamera.position.copy( reflectedPosition );

				// grab the corners of the other portal
				// - note: the portal is viewed backwards; flip the left/right coordinates
				otherPortalMesh.localToWorld( bottomLeftCorner.set( 50.05, - 50.05, 0.0 ) );
				otherPortalMesh.localToWorld( bottomRightCorner.set( - 50.05, - 50.05, 0.0 ) );
				otherPortalMesh.localToWorld( topLeftCorner.set( 50.05, 50.05, 0.0 ) );
				// set the projection matrix to encompass the portal's frame
				CameraUtils.frameCorners( portalCamera, bottomLeftCorner, bottomRightCorner, topLeftCorner, false );

				// render the portal
				thisPortalTexture.texture.colorSpace = renderer.outputColorSpace;
				renderer.setRenderTarget( thisPortalTexture );
				renderer.state.buffers.depth.setMask( true ); // make sure the depth buffer is writable so it can be properly cleared, see #18897
				if ( renderer.autoClear === false ) renderer.clear();
				thisPortalMesh.visible = false; // hide this portal from its own rendering
				renderer.render( scene, portalCamera );
				thisPortalMesh.visible = true; // re-enable this portal's visibility for general rendering

			}

			function animate() {

				// move the bouncing sphere(s)
				const timerOne = Date.now() * 0.01;
				const timerTwo = timerOne + Math.PI * 10.0;

				smallSphereOne.position.set(
					Math.cos( timerOne * 0.1 ) * 30,
					Math.abs( Math.cos( timerOne * 0.2 ) ) * 20 + 5,
					Math.sin( timerOne * 0.1 ) * 30
				);
				smallSphereOne.rotation.y = ( Math.PI / 2 ) - timerOne * 0.1;
				smallSphereOne.rotation.z = timerOne * 0.8;

				smallSphereTwo.position.set(
					Math.cos( timerTwo * 0.1 ) * 30,
					Math.abs( Math.cos( timerTwo * 0.2 ) ) * 20 + 5,
					Math.sin( timerTwo * 0.1 ) * 30
				);
				smallSphereTwo.rotation.y = ( Math.PI / 2 ) - timerTwo * 0.1;
				smallSphereTwo.rotation.z = timerTwo * 0.8;

				// save the original camera properties
				const currentRenderTarget = renderer.getRenderTarget();
				const currentXrEnabled = renderer.xr.enabled;
				const currentShadowAutoUpdate = renderer.shadowMap.autoUpdate;
				renderer.xr.enabled = false; // Avoid camera modification
				renderer.shadowMap.autoUpdate = false; // Avoid re-computing shadows

				// render the portal effect
				renderPortal( leftPortal, rightPortal, leftPortalTexture );
				renderPortal( rightPortal, leftPortal, rightPortalTexture );

				// restore the original rendering properties
				renderer.xr.enabled = currentXrEnabled;
				renderer.shadowMap.autoUpdate = currentShadowAutoUpdate;
				renderer.setRenderTarget( currentRenderTarget );

				// render the main scene
				renderer.render( scene, camera );

			}

		</script>
	</body>
</html>